Apiano emits frequencies that range from a low of about 28 hertz to a high of about 4200 hz. find the range of wavelength in air attained by this instrument when the speed of sound in air in 342m /s

The solution for this problem is:
A velocity of wave is given as V = λ⋅f
V - velocity of wave
f - frequency of wave
λ -  wave length

So getting the wave length is:
λ = V/f
λminimum = V / fmaximum
λminimum = 342 / 4200
λminimum = 0.081 m

λmaximum = V/ fminimum
λmaximum = 342 / 28
λmaximum = 12.214 m

If its history of, then b) because a) implies only present day (now)